You cannot build great cities by consensus alone

When you want to drain a marsh," declared the late President Mitterrand, "you don't consult the frogs."

He was referring to the expansion of airports but he could equally have been talking of Baron Haussmann's creation of the famous Parisian boulevards for Napoleon III.

Whole neighbourhoods were wiped out without apology or discussion to create what are now among the City of Light's greatest glories.

We do things differently here in the land of the Magna Carta and, now, in the age of focus groups.

And so it is that we find Hank Dittmar, Prince Charles's principal architectural adviser, calling for more of something called "Enquiry by Design", which "allows local residents to actually design the masterplan of new communities".

Run by the Prince's Foundation, of which Dittmar is director, Enquiry by Design will "hand power to the people".

This in principle is fine and right and proper and good, even if not wholly original.

Careful and professional engagement of local communities has been practised for years on projects such as the redevelopment of King's Cross.

Planning applications now have to have something called "a statement of community involvement".

Lord Rogers, although Dittmar says he is "scared" of such things, called for them in his government report Towards an Urban Renaissance 10 years ago.

So why do Dittmar's comments inspire in me a certain queasiness? Why do they provoke a mistrust that they will not lead to quite such a rosy future as you might think? Why the sense that there is something missing here?

It's this: this great, marvellous, multi-faceted city was not created by workshops and communities designing things in groups.

Neither the city's monuments nor its ordinary streets and squares were made by people consuming tea and biscuits in community halls, wielding felt-tips and Post-it notes - the preferred tools of community design - on colourful plans.

Sir Christopher Wren didn't ask the booksellers of neighbouring Paternoster Row to guide his hand when he was designing St Paul's, nor did the then Duke of Westminster draw on the urban-design skills of the cabbage growers who occupied what is now Belgravia.

Nor did the more modest developers who made most of what is now London seek many opinions from the general public.

Architects and developers did not have it all their own way and Wren's wish to replan the City after the Great Fire was blocked by the landowners of the Square Mile, whose land holdings were ignored in Wren's geometrical layout of straight streets and avenues.

He also had to modify his designs for the cathedral in response to his clients, the dean and chapter. But he would have been incredulous at the idea of the public helping him in his work.

The ingredients that community design tends to suppress are invention and daring. It favours the already-known and the unobjectionable.

It is hard to imagine ideas that were once new, such as Burlington Arcade, or the Victorian railway stations, being created in this way.

Nor does it take into account the fact that buildings outlive people: architecture loathed by one generation is loved by the next, and the Georgian Bloomsbury that is now so admired was hated by, for example, Charles Dickens.

Had Bloomsbury been subjected to consultation, it might never have been built.

You also have to ask who "the public" are and what "the community" is.

These words suggest a happy band of like-minded people, who all want the same thing. Yet old rich people might want something different from young poor people.

The abandoned scheme for Chelsea Barracks was vociferously opposed by many, especially the well-heeled residents of nearby Belgravia, but supported by a significant number of residents of adjoining council blocks.

They wanted the open space and swimming pool promised by the developers.

There is no doubt that many people prefer old styles of architecture to new ones but polls to find people's favourite buildings are often won by modern designs such as the Gherkin, the London Eye or the Eden Project.

There is, in other words, no uniform taste. Whose voice, when places are designed by "the public", matters more?

The proposed redevelopment of King's Cross shows the strengths and weakness of high levels of public involvement.

The developer in charge, Roger Madelin, says he "stopped counting" after he had been to 350 meetings, and he hired a consultancy, called Fluid, to conduct admirably inventive and creative consultation events.

The resulting plans are scrupulous, professional and high-quality. They promise to be among the best of their kind.

But they still don't satisfy everyone and they also lack the daring that went into creating the great stations already on the site. There is a kind of normality to them.

Most significantly, the development is not there yet: the protracted processes of consultation mean that almost nothing has actually been built.

None of this is to say public opinion doesn't matter, or to decry the admirable processes of consultation that some developers and consultancies carry out.

Done well, talking to people can add to the richness of a design. It is particularly important that people are closely involved when the places where they actually live are being re-shaped - if a housing estate is being remodelled, for example.

It is progress that our planners are no longer as callous as Napoleon III and Haussmann, even if the places we build are less impressive than theirs.

What we don't need is more consultation than we have now, which is already more extensive than at any previous time in history.

Nor should we believe that public participation can make a city on its own.

Involving people can enrich and temper proposals but somebody has to propose, invent, decide and gamble, which committees and public gatherings can't do.

Planners, architects and developers have to propose what they think is good, which can then be scrutinised and challenged.

Often architects will propose buildings that some people don't like but this fact cannot be wished away by legislation.

You can't please everybody all the time. If you try to you risk pleasing nobody.

Cities such as London are about coexistence and tolerance, and accommodating conflict rather then suppressing it.

If Dittmar is just saying that people's opinions matter, I couldn't agree more, but if he believes that major projects can be designed by collective consensus, I beg to differ.